The primary objective of this research is to identify the compound responsible for the anti-tumor activity of the chloroform fraction of the ethanol extract of Isocoma Wrightii (Aplopappus heterophyllus). A second objective is the identification of the compound responsible for the toxicity of the "tremetol" fraction of the plant extract. The plant has been found to contain a family of benzofurans: toxol(2S, 3R-2-isopropenyl-3-hydroxy-5-acetyl-2,3-dihydrobenzofuran), toxyl angelate, tremetone (2S-isopropenyl-5-acetyl-2,3-dihydrobenzofuran), dehydrotremetone, 2,5-diacetylbenzofuran and toxethol (2-isopropenyl-3-hydroxy-5 (1'-ethoxyethyl) 2,3-dihydrobenzofuran). Some of these compounds show weak activity against PS tumors. Plant material collected in another locality was shown to contain 7-((3-methyl-2-butenyl)oxyl) coumarin. In addition, three novel sesquiterpenes have been isolated from I. Wrightii: isocomene (Chem. Comm. 456(1977)), modhephene, the first carbocyclic (3.3.3) propellane and 1,2,3,4-tetrahydro-1,1,5,6-tetramethylnaphthalene, a nordrimane. Likewise a group of steroids, triterpenes and fatty alcohols have been isolated and work is progressing on a small alkaloid fraction, which may contain the biologically active components.